Multithreading errors with Draw.Text

[Spiderbird]

Hi there,

I'm having a problem trying to render text on a blueprint chart. Here's what I'm using:

public class Ver14 : Strategy
    {​

//  Define custom fonts for use in this section
            NinjaTrader.Gui.Tools.SimpleFont Arial_7pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 7);
            NinjaTrader.Gui.Tools.SimpleFont Arial_8pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 8);
            NinjaTrader.Gui.Tools.SimpleFont Arial_9pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 9);
            NinjaTrader.Gui.Tools.SimpleFont Arial_10pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 10);
            NinjaTrader.Gui.Tools.SimpleFont Arial_12pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 12);
            NinjaTrader.Gui.Tools.SimpleFont Wingdings2_12pt = new NinjaTrader.Gui.Tools.SimpleFont("Wingdings 2", 12);
            NinjaTrader.Gui.Tools.SimpleFont Wingdings2_16pt = new NinjaTrader.Gui.Tools.SimpleFont("Wingdings 2", 16);

            // Freeze the colors we want to use
            Brush expensive_green = new SolidColorBrush(Color.FromArgb(0, 0, 100, 0));
            Brush bargain_green = new SolidColorBrush(Color.FromArgb(0, 0, 128, 0));
            Brush delta_green = new SolidColorBrush(Color.FromArgb(0, 203, 236, 181));
            Brush expensive_red = new SolidColorBrush(Color.FromArgb(0, 177, 14, 20));
            Brush bargain_red = new SolidColorBrush(Color.FromArgb(0, 221, 17, 25));
            Brush delta_red = new SolidColorBrush(Color.FromArgb(0, 255, 204, 203));​

protected override void OnBarUpdate()
        {​

//  Freeze the brushes we will be using in the script
                expensive_green.Freeze();
                bargain_green.Freeze();
                delta_green.Freeze();
                expensive_red.Freeze();
                bargain_red.Freeze();
                delta_red.Freeze();​


}  //  end of on bar update

private void chart_print_indicatorIcons()
        {      
        //  Green/Expensive
            if (delta_momentum_meter == 5 && price_momentum_meter == -5)
            {
                chart_counter++;        //  Increase the chart counter

                Draw.Text(this, chart_counter.ToString(), true, "q 444", 1,            //  Show a dark green arrow with three dollar signs to signal expensive buys    
                    Close[0], 1, expensive_green,                
                    Wingdings2_12pt, TextAlignment.Center,
                    Brushes.Transparent, Brushes.Transparent, 0);

            }

        //  Red/Expensive
            else if (delta_momentum_meter == -5 && price_momentum_meter == -5)
            {
                chart_counter++;        //  Increase the chart counter

                Draw.Text(this, chart_counter.ToString(), true, "444 w", 1,            //  Show a dark red arrow with three dollar signs to signal expensive sells    
                    Close[0], 1, expensive_red,                
                    Wingdings2_12pt, TextAlignment.Center,
                    Brushes.Transparent, Brushes.Transparent, 0);

            }​

(etc.)

----

I generate the following error on running the script:
Error on calling 'OnBarUpdate' method on bar 10: The calling thread cannot access this object because a different thread owns it.

For reference, "chart_print_indicatorIcons()" is called whenever there's a particular event in the code that gets triggered.

Also, I'm not sure where to place a Dispatcher.ASync reference in there, but please help me out if you could.

It's weird because I never encountered this in NT7.

Thanks in advance!

[Leeroy_Jenkins]

My guess is that you need call chart_print_indicatorIcons() using TriggerCustomEvent.

[QuantKey_Bruce]

You didn't encounter it in NT7 because it wasn't multithreaded in this way in NT7. You don't need to freeze fonts, but you need to freeze brushes. You should freeze them immediately after you created them, not later in OnBarUpdate. It has to be done before you get to OnRender or OnBarUpdate - if you're creating them in OnStateChange you should freeze them right there before it exits that method. If you're creating them at the top, you have a problem, because it could run OnRender before they get frozen and that's in a different thread.

I would suggest rather than instantiating the brushes there at the top, you just declare the variables and don't set a value or set them to null, and then in OnStateChange under State.Configure or State.DataLoaded, set them equal to the new SolidColorBrush(whatever) and then freeze them. Don't do it at the top, and don't fail to freeze them before you leave OnStateChange. If you do these things, it should work without this failure.

[Spiderbird]

You didn't encounter it in NT7 because it wasn't multithreaded in this way in NT7. You don't need to freeze fonts, but you need to freeze brushes. You should freeze them immediately after you created them, not later in OnBarUpdate. It has to be done before you get to OnRender or OnBarUpdate - if you're creating them in OnStateChange you should freeze them right there before it exits that method. If you're creating them at the top, you have a problem, because it could run OnRender before they get frozen and that's in a different thread.

I would suggest rather than instantiating the brushes there at the top, you just declare the variables and don't set a value or set them to null, and then in OnStateChange under State.Configure or State.DataLoaded, set them equal to the new SolidColorBrush(whatever) and then freeze them. Don't do it at the top, and don't fail to freeze them before you leave OnStateChange. If you do these things, it should work without this failure.

Hi Bruce!

That worked! But now I have a different problem. All of the text is showing up is white. It's not colored when using Color.FromArgb (or Color.FromRgb)
It DOES work when I just use regular brush colors (Brushes.DarkRed), but not RGB)

Here's what I have:

(before onBarUpdate and onStateChange:

//  Define custom fonts for use in this section
            NinjaTrader.Gui.Tools.SimpleFont Arial_7pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 7);
            NinjaTrader.Gui.Tools.SimpleFont Arial_8pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 8);
            NinjaTrader.Gui.Tools.SimpleFont Arial_9pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 9);
            NinjaTrader.Gui.Tools.SimpleFont Arial_10pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 10);
            NinjaTrader.Gui.Tools.SimpleFont Arial_12pt = new NinjaTrader.Gui.Tools.SimpleFont("Arial", 12);
            NinjaTrader.Gui.Tools.SimpleFont Wingdings2_12pt = new NinjaTrader.Gui.Tools.SimpleFont("Wingdings 2", 12);
            NinjaTrader.Gui.Tools.SimpleFont Wingdings3_16pt = new NinjaTrader.Gui.Tools.SimpleFont("Wingdings 3", 16);

            Brush expensive_green = null;
            Brush bargain_green = null;
            Brush delta_green = null;
            Brush expensive_red = null;
            Brush bargain_red = null;
            Brush delta_red = null;​

On state change in DataLoaded (also tried State.Configure)

 if (State == State.DataLoaded)  
                {
                    // Set the colors we want to use for our brushes
                    Brush expensive_green = new SolidColorBrush(Color.FromRgb(0, 100, 0));
                    Brush bargain_green = new SolidColorBrush(Color.FromRgb(0, 128, 0));
                    Brush delta_green = new SolidColorBrush(Color.FromRgb(203, 236, 181));
                    Brush expensive_red = new SolidColorBrush(Color.FromRgb(177, 14, 20));
                    Brush bargain_red = new SolidColorBrush(Color.FromRgb(221, 17, 25));
                    Brush delta_red = new SolidColorBrush(Color.FromRgb(255, 204, 203));

                    //  Freeze these brushes
                    expensive_green.Freeze();
                    bargain_green.Freeze();
                    delta_green.Freeze();
                    expensive_red.Freeze();
                    bargain_red.Freeze();
                    delta_red.Freeze();
                }​

in OnBarUpdate, where a method is called to display text:

private void chart_print_indicatorIcons()
        {      
        //  Green/Expensive
            if (delta_momentum_meter == 5 && price_momentum_meter == -5)
            {
                chart_counter++;        //  Increase the chart counter

                Draw.Text(this, chart_counter.ToString(), true, "Green/Expensive", 1,            //  Show a dark green arrow with three dollar signs to signal expensive buys    
                    Close[0], 1, expensive_green,                
                    Arial_12pt, TextAlignment.Center,
                    Brushes.Transparent, Brushes.Transparent, 0);

            }

        //  Red/Expensive
            else if (delta_momentum_meter == -5 && price_momentum_meter == -5)
            {
                chart_counter++;        //  Increase the chart counter

                Draw.Text(this, chart_counter.ToString(), true, "Red/Expensive", 1,            //  Show a dark red arrow with three dollar signs to signal expensive sells    
                    Close[0], 1, expensive_red,                
                    Arial_12pt, TextAlignment.Center,
                    Brushes.Transparent, Brushes.Transparent, 0);​

(etc.)

Attachment shows the white text to the left of the blueprint chart prints.

[NinjaTrader_ChrisL]

Hi Spiderbird, you are defining your brushes within OnStateChanged within State.DataLoaded, so the scope is limited to only OnStateChanged. You will need to move the brush variable decalration to the class level and initialize it in State.DataLoaded, then freeze it.

//Class level
Brush expensive_green;

//in OnStateChanged, DataLoaded:
expensive_green = new SolidColorBrush(Color.FromRgb(0, 100, 0));
expensive_green.Freeze();

[QuantKey_Bruce]

Yes, just remove the word Brush from those lines so it's not overloading the class field expensive_green with a local one which is then disposed at the end of the method scope.

[Spiderbird]

Hi Spiderbird, you are defining your brushes within OnStateChanged within State.DataLoaded, so the scope is limited to only OnStateChanged. You will need to move the brush variable decalration to the class level and initialize it in State.DataLoaded, then freeze it.

//Class level
Brush expensive_green;

//in OnStateChanged, DataLoaded:
expensive_green = new SolidColorBrush(Color.FromRgb(0, 100, 0));
expensive_green.Freeze();

That did the trick! I feel a bit dumb for putting Brush in there twice without realizing it.
Thanks for your timely help, and I hope you both are doing well.